Macrophages are a major source of NF-kappaB-dependent cytokines and chemokines that are involved in the systemic response to gram-negative endotoxemia. The contribution of macrophage derived COX-2 expression to the pathogenesis of the endotoxin response is unknown. In this proposal, we will focus on two interrelated hypotheses: 1) Neutrophilic inflammation in the lung and liver is mediated by NF- kappaB-dependent signaling events that originate in macrophages. 2) COX-2 gene expression in macrophages has a major regulatory impact on NF-kappaB dependent cytokine production and the development of endotoxin-induced neutrophilic lung and liver inflammation. We propose three specific aims: 1) to determine the extent of macrophage COX-2 gene expression in endotoxin-induced neutrophilic lung and liver inflammation. Novel transgenic mice with a COX-2 promoter driving luciferase and GFP reporter genes will be used to define the effect of treatment 2) to determine whether elimination of macrophage COX-2 gene expression and/or production of COX-2 of COX-2 metabolites influence the generation of neutrophilic lung and liver inflammation in response to exposure of mice to endotoxin. This will be done by bone marrow transplantation of COX-2 deficient donor mice to selectively deplete COX-2 expression in myeloid-derived of recipient wild-type mice. 3) to investigate the effects of macrophage-restricted COX-2 transgene expression on the magnitude and duration of the endotoxin response in whole animals. Macrophage restricted transgene expression will be accomplished using a novel promoter based on macrophage restrictive elements of the macrophage mannose receptor promoter. These studies are unique because they employ specific and comprehensive approach to identifying the role of macrophage-derived COX-2 gene expression in a while animal model. A more complete understanding of the pathogenesis of inflammation associated with endotoxemia should lead to new effective treatments and improved survival.